Unwrapping a cube for multiple textures?
Yes.  You do need two materials.  I would make two materials, and two material slots.  To make slots you press the plus beside the materials list in the material tab.  You should see another sphere appear in the list.  Then, assign the new material the top image texture.  After that, in  edit mode, select the top faces.  With them selected, then select the new material you just made in the list, then click assign.  Then, you can unwrap the top faces, or you can use your existing unwrap and replace the original image with the new top one.

Don't call yourself a noob.  We all start somewhere. :)